A known rotational drive apparatus includes an electric motor and a speed reducer, which are coaxially placed in a housing. The known rotational drive apparatus reduces a rotational speed of rotation, which is outputted from a motor shaft of the electric motor, through the speed reducer, and the known rotational drive apparatus outputs the rotation of the reduced rotational speed.
For example, JP2011-27254A (corresponding to US2012/0100949A1) discloses a speed reducer that includes a planetary gear apparatus. An internal gear of the planetary gear apparatus is formed integrally with a housing.
In JP2011-27254A (corresponding to US2012/0100949A1), a motor shaft of an electric motor is supported by a separate member, which is formed separately from the internal gear of the planetary gear apparatus. Therefore, there is a limit with respect to improvement of coaxiality between the internal gear and the motor shaft.
Although not recited in JP2011-27254A (corresponding to US2012/0100949A1), it is conceivable to form a support device, which supports the motor shaft, in a portion of the housing. However, in order to accurately form the internal gear and the support device in the housing, the number of manufacturing steps and the costs are disadvantageously increased. Furthermore, it is difficult to install the motor to such a housing.